The present invention relates to optical communication equipment and network equipment, such as optical communication equipment and network equipment comprising a semiconductor laser element, an optical fiber, an optical detector and an optical system for optically coupling them.
In optical communication equipment which couples an output from a semiconductor laser element to an optical fiber and transmits information to a distant place, it is necessary to couple the output from the semiconductor laser element to the optical fiber as efficiently as possible.
To meet the demands of size reduction and surface mounting in such optical modules, optical components are mounted within a dual in-line type package as in the case of integrated circuits (ICs) and large-scale integrated circuits (LSIs), and then the package is mounted on a circuit board.
Within the package, the optical components and other components are mounted on a Si substrate.
In the optical coupling system, as a coupling lens for coupling light from the semiconductor laser element to the optical fiber, a ball-type spherical lens 1 is used as illustrated in FIG. 1. The ball-type spherical lens is described in xe2x80x9cLIGHTWAVExe2x80x9d by J. F. Dormer, p82, February 1998.
In the conventional ball-type lens, there is a problem that, when its numerical aperture on a semiconductor laser element side is increased for improving optical coupling efficiency, its spherical aberration increases, increase in the spherical aberration degrades a light spot profile on the entrance end of the optical fiber, and consequently decreases its optical coupling efficiency to the optical fiber.
There is another problem with the conventional ball-type lens that, when a light spot of the semiconductor laser element is displaced from the optical axis of the ball-type lens, coma aberration, astigmatism and spherical aberration in a narrow sense occur, and the optical coupling efficiency is made smaller than when the light spot on the optical axis of the ball-type lens.
It is one of the objects of the present invention to solve the above problems. One of features in an embodiment of the present invention is such that an optical component having a better imaging characteristics in place of the ball-type lens is mounted on a Si substrate on which a semiconductor laser element is also mounted. A V-groove having a substantially xe2x80x9cVxe2x80x9d-shaped cross-section is formed in the Si substrate with unisotropic etching.